1. Field of the Invention
The invention relates to a sheet feed cassette that is installed within a sheet feeder system of an image forming apparatus such as a printer, e.g. a laser printer or a copier, e.g. a xerographic copying apparatus, that is used to feed and forward sheets toward the image transfer section of such apparatus one by one. More particularly, the invention is directed to a single sheet feed quadruple cassette capable of holding and feeding up to four separate reams (stacks) of paper, and is also directed to a method for feeding up to four separate reams (stacks) of paper from a single cassette.
2. Description of the Prior Art
Generally speaking, the process of electrostatographic reproduction can be employed in a printer or a copier and basically includes initially charging a photoconductive member to a substantially uniform potential so as to sensitize the surface thereof. A charged portion of the photoconductive surface is then exposed at an exposure station to a light image of an original document that is to be reproduced. Typically, an original document that is to be reproduced is placed in registration, either manually or by means of an automatic document handler, on a platen for such exposure.
By exposing an image of an original document as such at the exposure station, there is recorded an electrostatic latent image of the original image onto the photoconductive member. The recorded latent image is subsequently developed using a developmental apparatus by bringing a charged dry or liquid developer material into contact with the latent image. Two component and single component developer materials are commonly used. A typical two-component dry developer material has magnetic carrier granules with fusible toner particles adhering triobelectrically thereto. A single component dry developer material that typically comprises toner particles only can also be used. The toner image formed by such a development process is subsequently transferred at a transfer station onto a copy sheet fed to such transfer station. The toner particles image on the copy sheet is then heated and permanently fused so as to form a xe2x80x9chardcopyxe2x80x9d of the original image. The copy sheet typically is then fed from a copy sheet supply that can be an elaborate and expensive elevator assembly, or a relatively less costly cassette tray assembly, such as for example, a forward feed buckle cassette tray assembly. There are several different structures for cassette tray assemblies known in the art. Examples of some of these different structures are illustrated in the following U.S. Patents:
U.S. Pat. No. 5,224,693 describes a copying machine including a paper feeding device that has a paper feeding cassette which can be divided into first and second trays in tandem in a paper feeding direction within the copying machine body. The paper feeding device also has several feeding trays vertically stacked with regard to each other.
U.S. Pat. No. 5,102,112 describes a paper feeding cassette that is divided into two paper sections that are in tandem to one another.
U.S. Pat. No. 5,405,128 illustrates a sheet feed device having a tray provided with two sheet storing portions adjoining each other serially in the direction of sheet feed. Sheet feeding and separating means are both associated with each of t he sheet storing portions to direct the sheets one by one to a copier. A transport device drives the sheet fed out from the rear storing portion of a tray to a vertical transport path.
One of the most important and significant advantages that one printer can have over another printer, or that one xerographic copier can have over another xerographic copier, is a larger paper feeder capacity. This is a significant feature at all price levels of printers/copiers. Typically, a single cassette holds one ream of #20 paper. A standard midvolume machine has 4 cassettes and can therefore hold up to four (4) reams of paper (e.g. #20 paper). Additional sheet capacity is obtained by the use of an attached high capacity feeder module. However, these separate paper feeder modules which supply extra paper to the copier/printer have the disadvantage of being relatively expensive, and very bulky. They also require a good deal of space when added to a copier/printer. Currently available to try to overcome this disadvantage, are tandem cassettes, which hold two (2) reams of paper. These are loaded in a long edge feed direction. When all the paper in the first stack has been used, the second stack is moved into feed position.
It is a primary objective of the present invention to overcome all of the disadvantages referred to above in a paper supply cassette for use in a printer or copier apparatus.
In accordance with the features of the present invention there is provided a quadruple capacity cassette structure which eliminates all of the basic disadvantages referred to above, and provides at a reasonable cost and within a reasonable amount of space a sheet feed cassette for an apparatus such as a printer or a copier, that is adapted to be installed within a sheet feed unit of an image forming apparatus and feed a very large volume of paper to the apparatus. The cassette structure comprises a frame including at least a side frame and a bottom frame; a bottom plate provided above the bottom frame including collapsible guide walls for positioning four separate stacks of sheets within the cassette, each of the walls adapted to collapse thereby allowing each of the four stacks to be moved within the cassette to a position in contiguous relation to a feeder unit for feeding individual sheets from a single stack of sheets positioned within the cassette into the apparatus; and a feeding device to move each of the four stacks from different positions within the cassette to a position in contiguous relation to the feeder unit so that individual sheets can be fed to the apparatus from each of the four stacks.
In accordance with additional features of the present invention there is provided a method for feeding sheets from separate stacks of sheets positioned in a cassette, the cassette being adapted to be installed within a sheet feed unit of an image forming apparatus. The method comprises the steps of: (a) positioning four separate stacks of sheets within areas of the cassette having collapsible guide walls; (b) collapsing some of the guide walls in a timed relationship whereby each of the four separate stacks is free to move within the cassette towards the sheet feeder unit; (c) moving each of the four stacks in a timed relationship so that each stack is positioned in a contiguous relation to a sheet feeder unit for feeding individual sheets from a single stack of sheets; (d) feeding a sheet one at a time from each of the stacks to the apparatus as each stack is positioned at the feeder unit.
Furthermore in accordance with additional features of the present invention there is provided a method for feeding sheets from four separate stacks of sheets positioned in a cassette and separated by collapsible walls, the cassette being adapted to be installed within a sheet feed unit of an image forming apparatus. The method comprises the steps of: (a) positioning a first stack of sheets within the cassette whereby sheets can be fed by a feeder unit into the apparatus; (b) collapsing a wall separating the first stack of sheets from a second stack of sheets; (c) moving the second stack of sheets within the cassette whereby sheets from the second stack can be fed by the feeder unit into the apparatus; (d) collapsing a wall separating a third stack of sheets from the original position of the first stacks of sheets; (e) moving the third stack of sheets within the cassette whereby sheets from the third stacks can be fed by the feeder unit into the apparatus; (f) collapsing a wall separating a fourth stack of sheets from the original position of the second stack of sheets; and (g) moving the fourth stack of sheets within the cassette whereby sheets from the fourth stack of sheets can be fed by the feeder unit into the apparatus.